Interesting, I just bought some worm castings myself. I have a Hunt fig that I received from JF&E in the fall and am going to move it to a 6.5 gallon SWC (self watering container) this weekend. I plan on adding some worm castings (1 cup) to the potting mix. It can't hurt and it can only help.
My opinion is that new cuttings might be a bit early to try worm castings and perlite only. Of course, if you want to experiment and report your results like many members do here, go for it.
Many members are not as lucky as us to be blessed with very high humidity : ) You would have to time your cuttings to coincide with the high humidity in the late spring / summer. Well, then there is the other concern. When the humidity gets high so do the temperatures and the cuttings might bake in the heat even in the shade. You did make me think of another experiment though, I'm going to try starting some cuttings this summer directly in 1 gallon nursery pots outside.